The present invention relates to a method of forming silica-containing ceramic coatings on substrates such as electronic devices. These coatings can be used to provide hermetic protection to the underlying substrate or they can be used as dielectric layers.
The use of hydrogen silsesquioxane derived ceramic coatings on substrates such as electronic devices is known in the art. For instance, Haluska et al. in U.S. Pat. No. 4,756,977 disclose a process for forming silica-containing coatings on substrates such as electronic devices. The process described therein involves applying a solution of hydrogen silsesquioxane resin on a substrate followed by heating the coated substrate in air at a temperature in the range of 200.degree.-1000.degree. C. Since temperatures in the range of 600.degree.-800.degree. C. are required for complete conversion of the hydrogen silsesquioxane resin to silica, the method has limited utility when temperature sensitive substrates such as electronic devices are to be coated.
Other methods for converting hydrogen silsesquioxane resin to silica-containing materials at lower temperatures are also known in the art. For instance, U.S. Pat. No. 4,847,162 describes the conversion of hydrogen silsesquioxane resin to nitrified silica by heating in ammonia. Similarly, U.S. Pat. No. 5,116,637 describes the use of amines to assist in the conversion of hydrogen silsesquioxane resin to silica-containing materials. The agents used in these processes, however, may be corrosive or may present disposal concerns which limit their use in certain industry.
The present invention discloses that certain silicon hydride containing materials can be converted to silica-containing coatings at low temperatures by heating in an environment containing nitrous oxide.